Customer.io

Customer.io Newsletter Variants API

A newsletter variant is a translation or an A/B test. You can create, update, or delete variants in newsletters from these endpoints. You can also create a new A/B test group. If your newsletters include assets like images or PDFs, host them in your [workspace's assets](/integrations/api/app/#tag/assets) or at another public URL, and include the URL in your message content.

GitHub OpenAPI

Operations 13

GET /v1/newsletters/{newsletter_id}/contents List newsletter variants #
GET /v1/newsletters/{newsletter_id}/contents/{content_id} Get a newsletter variant #
PUT /v1/newsletters/{newsletter_id}/contents/{content_id} Update a newsletter variant #
POST /v1/newsletters/{newsletter_id}/language Add a translation to a newsletter #
GET /v1/newsletters/{newsletter_id}/language/{language} Get a newsletter translation #
PUT /v1/newsletters/{newsletter_id}/language/{language} Update a translation of a newsletter #
DELETE /v1/newsletters/{newsletter_id}/language/{language} Delete a translation of a newsletter #
GET /v1/newsletters/{newsletter_id}/test_groups List a newsletter's A/B test groups #
POST /v1/newsletters/{newsletter_id}/test_groups Create an A/B test group for a newsletter #
POST /v1/newsletters/{newsletter_id}/test_group/{test_group_id}/language Add a translation to a newsletter test group #
GET /v1/newsletters/{newsletter_id}/test_group/{test_group_id}/language/{language} Get a translation in a newsletter test group #
PUT /v1/newsletters/{newsletter_id}/test_group/{test_group_id}/language/{language} Update a translation in a newsletter test group #
DELETE /v1/newsletters/{newsletter_id}/test_group/{test_group_id}/language/{language} Delete a translation in a newsletter test group #

Documentation

📖
Documentation
https://docs.customer.io/integrations/api/app/
📖
Documentation
https://docs.customer.io/integrations/data-in/connections/http-api/

Specifications

⚙
OpenAPI
https://raw.githubusercontent.com/api-evangelist/customer-io/refs/heads/main/openapi/customer-io-newsletter-variants-api-openapi.yml

Work with this as data

Every API here is available over the APIs.io API and to AI agents over MCP.

MCP server

One button, every client — Claude, Cursor, VS Code and the rest.

https://apis.io/mcp

Tools for apis

7 MCP tools reach this
  • find_apisBrowse and filter every API in the catalog.
  • get_api_artifactsOne API's artifacts, grouped by type.
  • get_openapiThe primary OpenAPI for this API.
  • find_similar_apisAPIs that look like this one.
  • apis_io_searchSTART HERE — APIs, providers and tags for one query, each with its total.
  • resolveTurn a domain, URL or GitHub org into the provider it belongs to.
  • find_cohortsEvery scored population of providers in the catalog.
All 92 tools →

Call it yourself

curl for this page
This API 
curl "https://apis.io/api/v1/apis/customer-io-newsletter-variants-api"
All apis 
curl "https://apis.io/api/v1/apis?limit=25"

Discovery needs no key. Ratings and market analysis are Pro.

Get an API key

Free tier, no form to fill in. Signing in shares your email address with us — we store it to create your key and to recognise you if you sign in with another provider. See our Privacy Policy and Terms.

GitHub Google LinkedIn

A second provider on the same verified email joins the account you already have.

OpenAPI Specification

customer-io-newsletter-variants-api-openapi.yml Raw ↑ 
openapi: 3.2.0
info:
  version: 1.0.0
  title: Customer.io App Newsletter Variants API
  description: Our App API provides ways to trigger messages and retrieve information about people, campaigns, broadcasts, and more.
servers:
- url: https://api.customer.io
  description: The base URL for broadcasts, transactional messages, and data-retrieval APIs. These endpoints use bearer authorization, and require a [token that you generate in the UI](https://fly.customer.io/settings/api_credentials?keyType=app).
- url: https://api-eu.customer.io
  description: The base URL for broadcasts, transactional messages, and data-retrieval APIs (EU region). These endpoints use bearer authorization, and require a [token that you generate in the UI](https://fly.customer.io/settings/api_credentials?keyType=app).
tags:


# --- truncated at 32 KB (144 KB total) ---
# Full source: https://raw.githubusercontent.com/api-evangelist/customer-io/refs/heads/main/openapi/customer-io-newsletter-variants-api-openapi.yml